lecture 3 cell biology

8/8/2019 Lecture 3 Cell Biology

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Questionsin

Cell Biolog


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(6) The formation of large biological moleculesfrom smaller building blocks releases

(7) A cell makes a large number of polymersfrom a small group of ..

(8) Proteins are made from only 20 different., while, DNA is built from four kinds of ..

WATER

MONOMER

Amino Acid

Nucleotides


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(9).... simple lipids that containadditional elements such as phosphorus, nitrogen,sulfur, or small hydrophilic organic compounds

(10).. is commonly used as a building block of more structurally complex lipids

(11). Is a steroid that plays asignificant role in the structure of the cellmembrane and from which we synthesize sex

hormones and vitamin D2

Complex lipid

Fatty Acids

Cholesterol


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(12) Lipids in water can generate three mostcommon configurations ...,.., ..

(12) Sugar monomers are .., suchas glucose, mannose and fructose

(13) Plants store .. as energy storage,while animals store ..

(14) Monosaccharide that have five carbonatoms are called ..

LiposomeMicelle Bilayer sheet

Monosaccharide

StarchGlycogen

Pentoses


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(15). carbohydrates containingseveral monosaccharides

(16) Is a polysaccharide used byinsects and crustaceans to build an exoskeleton

(7).. is a polymer of glucose thatforms plant cell walls

Oligosaccharide

Chitin

Cellulose


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Unlinkedmonomer Short polymer

(2)

(3)Hydrolysis

(1)

Polymer

Dehydration

(4)

(5)

(6)

LiposomeMicelle

Bilayer sheet


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Pr otein-Are polymer built from 20 different amino acid

(monomers)

- Are the most abundant macromolecules in cells

-R epresent more than 50% of the dry mass of cells

-H ave an important structural and enzymatic roles

-Transmit information (messages) between cells (protein

hormones)


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- Proteins embedded in the plasma membrane formchannels that control the passage of small moleculesinto and out of the cell- Provide a defense against infection (antibodies)-Transport and store other molecules such asoxygen- G enerate movement- Transmit nerve impulses- Control growth and differentiation

Pr otein


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Pr otein functionPr

oteins divided into two groups based on its function in the cells:

Str uctu r al p r oteins: Integ r al pa r ts of cellula r st r uctu r es (Fib r ousp r oteins (Collagen) , ca r tilage, skin and bone (ke r atin ), tubulin,actin like p r oteins, mic r otubules and, Mic r ofilaments

Dynamic p r oteins : Catalytic p r oteins; catalysts fo r chemicalr eactions, cell metabolism (ho r mones , insulin, e r th r p r otein andthy r oxine, hemoglobin-hemocyanin-myoglobin


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Am ino A c idsMost consist of carbon, hydrogen, oxygen, and nitrogen; 2contain sulfur, 1 contains seleniumAll contain two important functional groups:

Carboxylic acid group ( -COO H)Amino group ( - NH 2)


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T he side chain is the most impo r tant in dete r mining itscont r ibution to p r otein st r uctu r e and activity


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P eptide bond

Amino acid monomers held together by covalent bonds ( peptide bonds )T his bond links the ca r boxyl g r oup of one amino acidto the amino g r oup of the next amino acid


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Polypeptides: thousands or millions of amino acidsH

ave two distinct ends:Amino group (the amino - or N - terminus)Carboxylic group (carboxyl or C -terminus)

Protein consists of a specific amino acid sequenceThe amino acid sequence of protein determines its three

dimensional structure and its chemical reactivity .


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C onjugated proteins

A conjugated protein is a protein that functions ininteraction with other chemical groups

Nucleoproteins: chromosomeChromoprotein: haemoglobin

Phosphproteins: found in milk

G lycoproteins : contain oligosaccharide chainscovalently attached to their polypeptide side -chains, they play a role in cell -cell interactions

L ipioproteins: enzymes, transporters


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Leve ls of protein stru c tureProtein can have four levels of structure

1- Primary structure

2- Secondary structure

3-Tertiary structure

4-Q uaternary structure

Four Leve ls of P rotein S tru c ture

Am ino a c ids

P rim ary stru c ture

A lpha he lix

Hydrogenbond

Se c ondary stru c ture

P leated sheet

P o lypeptide(sing le subunitof transthyretin)

Tertiary stru c ture


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Primary structureP rimary structure : sequence of amino acids in a polypeptide-The correct amino acid sequence is determined by the cells

genetic information-The slightest change in this sequence affects the proteins ability

to function-Sickle cell disease is manifested by an inability of hemoglobin in

red blood cells to carry oxygen, the primary function of hemoglobin.

-This blood disorder is the result of change in a single amino acid


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Secondary structureS econdary structure : the regular arrangement of amino acidswithin localized regions of the polypeptideFolds in polypeptide that form a more stable structure, often

involving h ydrogen bonding between R grou psThere are two types of secondary structure:

H elical structure called an alpha helix ( -h elix ) (region of polypeptide chain coils around itself P leated sh eet ( sh eet ): two parts of polypeptide chain lie side

by side with hydrogen bonds between them.


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Tertiary structureT ertiary structure : additional folding of polypeptide to result ingreater stability and unique three -dimensional shape

Forms exposed regions or grooves in the molecule that areimportant for binding other moleculesD isulfide bonds : bonds between -SH groups from two different

amino acidsI n most p roteins combination of alpha helix and beta sheetsconnected by loop regions of polypeptide chain, fold into compactglobular structures called Domains (the basic unit of tertially structure )


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Quaternary structureQuaternary structure: occurs in proteins composed of two or more

polypeptides Subunit: each polypeptide in the protein, held together by

either/both covalent and noncovalent linkages

Homodimer: protein containing two identical subunits Heterodimer: protein containing two nonidentical subunits


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Good Luck

Dr Mona


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T he sphe r ical st r uctu r e is induced by thep r otein's te r tia r y st r uctu r e. T he molecule'sapola r (hyd r ophobic) amino acids a r ebounded towa r ds the molecule's inte r io r whe r eas pola r (hyd r ophilic) amino acids a r ebound outwa r ds

lecture 3 cell biology

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